1. Field of the Invention
The present invention relates to a engine-start discriminating apparatus for an internal combustion engine mounted on, for instance, an automobile.
2. Discussion of Background
In a conventional engine-start discriminating apparatus disclosed in, for instance, Japanese Unexamined Patent Publication 107034/1980, the starting of an internal combustion engine (hereinbelow, referred to as an engine) has been generally discriminated by detecting that the revolution number has increased to a predetermined number or more. A revolution number detecting means used for detecting a predetermined revolution number is disclosed in, for instance, Japanese Unexamined Patent Publication 212643/1985, and it will be described with reference to FIG. 6.
In FIG. 6, a reference numeral 1 designates an air cleaner, a numeral 2 designates air-flow meter to detect an amount of air to be sucked, a numeral 3 designates a throttle valve, a numeral 4 designates an intake manifold, a numeral 5 designates a cylinder, a numeral 6 designates a water temperature sensor to detect the temperature of cooling water for the engine, a numeral 7 designates a crank angle sensor, a numeral 8 designates an exhaust manifold, a numeral 9 designates an exhaust gas sensor to detect the concentration of an exhaust gas component (such as the concentration of oxygen), a numeral 10 designates a fuel injection valve, a numeral 11 designates an ignition plug, and a numeral 12 designates a control device.
The crank angle sensor is adapted to output a reference position pulse at every reference position of the crank angle (for instance, every 180.degree. for a four cylinder engine and every 120.degree. for a six cylinder engine) and to output a unit angle pulse at every unit angle (for instance, every 1.degree.). The control device 12 counts the number of the unit angle pulses upon receiving a reference position pulse to thereby obtain the crank angle. Further, a revolution speed of engine is obtainable by measuring the frequency or the period of the unit angle pulses.
In the apparatus shown in FIG. 6, the crank angle sensor 7 is installed in a distributor.
The control device 12 is constituted by a microcomputer consisting, for instance, of a CPU, a RAM, a ROM, and an input/output interface and so on.
The control device 12 receives a signal of intake air quantity S.sub.1 from the air-flow meter 2, a signal of water temperature S.sub.2 from the water temperature sensor 6, a crank angle signal S.sub.3 from the crank angle sensor, and a signal of exhaust gas S.sub.4 from the exhaust gas sensor 9. The control device 12 also receives a signal of battery voltage and a signal indicative of the throttle valve being fully closed although the signals are not shown in FIG. 6. The control device operates with reference to the input signals to calculate a fuel injection quantity to be supplied to the engine, whereby a fuel injection signal S.sub.5 is generated. The signal S.sub.5 actuates a fuel injection valve 10 to thereby feed a predetermined amount of fuel to the engine. In particular, when the engine is started, (i.e. in cranking operation caused by a starter), a thick mixture gas containing a large amount of fuel is supplied. When the starting of the engine is discriminated by the revolution number detecting means which detects the fact that the revolution number of the engine has increased, the gas mixture is made thin to be an air-fuel ratio suitable for the operation of the engine after starting, and the throttle valve, which is opened for idling operations, is further opened for warming operations.
In the conventional apparatus, when the starting of the engine is discriminated by detecting the increase of the revolution number, it takes time until the engine reaches a predetermined increased number of revolution, whereby discrimination of the starting of the engine is delayed and quick control can not be obtained.